1. Field of the Invention
The present invention relates to an additive composition suitable for use in the compounding of a granular detergent. More specifically, the present invention relates to an additive composition for a granular detergent, especially for a granular detergent containing an anionic surfactant, capable of providing an excellent soft finish or touch in fabrics to be washed while simultaneously washing the fabrics during a fabric laundering operation.
2. Description of the Prior Art
Heretofore, when fabrics are washed at home, a soft finish has generally been afforded to fabrics by first washing fabrics with conventional detergents and, then, treating the fabrics with a softening agent containing as a main ingredient a cationic surfactant such as a quaternary ammonium salt after rinsing the washed fabrics with a large amount of water. However, these soft finishing operations are troublesome and time-consuming. Accordingly, it is desired by consumers to develop a detergent composition capable of simultaneously washing and softening fabrics to be washed.
It is known that only slightly water-soluble di (long chain alkyl) type quaternary ammonium salts can exhibit an excellent soft finish and antistatic effects in fabric laundering operations. However, when di (long chain alkyl) type quaternary ammonium salts are used together with detergent compositions, it is difficult to obtain the desired soft finish and antistatic effects in the case of cotton fabrics, although softening effects can be obtained in the case of synthetic fiber fabrics (e.g., nylon and polyester fabrics). This is because, since home laundering detergents generally contain as a main ingredient anionic surfactants, quaternary ammonium salts added to the laundering system are attacked by the anionic surfactants in the detergents before the quaternary ammonium salts are absorbed into cotton fabrics. As a result, the quaternary ammonium salts loose their ionic properties and are stably dispersed in the laundering system and, therefore, it becomes difficult for the quaternary ammonium salts to be absorbed into cotton fabrics. Thus, the desired soft finish effects cannot be obtained.
Various attempts have been made to provide the desired softening effects in cotton fabrics even when quaternary ammonium salts are added to detergent solutions during fabric laundering operations. For instance, it has been proposed that quaternary ammonium salts be granulated or coated with inorganic or organic salts, or organic dispersing retarders to retard the swelling and dispersion of the quaternary ammonium salts in the detergent solution, as disclosed in Japanese Examined Patent Publication (Kokoku) No. 36-8927, U.S. Pat. No. 4073735, and Japanese Unexamined Patent Publication (Kokai) Nos. 55-86895, 53-41312, and 49-98403. However, the softening effects in cotton fabrics obtained from these methods are still insufficient, although a certain degree of improvement is obtained.